Weight is not an issue with them as much as size is.
That being said,on four seperate occasions they shippped a Gas pump,8ft. lamp post,Full Chevelle 1/4 panel in the box and a 5ft.Trico wiper cabinet for me in the past.Don't underestimate them,as they don't want to advertise this publicly like UPS,but they really want this business.
Also look at
http://www.uship.com